Drill string stabilizer



Sept. 10, 1963 c. H. LEATHERS 3,103,391

DRILL STRING STABILIZER Filed Feb. 18. 1960 .wf/v7 v vv@ WA v CLAQENCE Hi 5477/5195, INVENToR.

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United States Patent 3,103,391 DRILL STRING STABILIZER Clarence H. Leathers, 3010 Johnson Ave., Redondo Branch, Calif. Filed Feb. 18, 1960, Ser. No. 9,646 3 Claims. (Cl. 308-4) This invention relates generally to drill pipe stabilizers which are adapted to be attached onto rotary drill strmgs and particularly onto drill collars for engagement with the wall of a well in lateral stabilizing relationship with the string, and more particularly with an improved stabilizer having a combination of metallic and elastomeric wear surfaces.

In a drilling operation wherein one or more stabilizers are used on the drill string, and particularly on the drill collars, at a location in the well, it is frequently necessary to wash over the string and past the stabilizers, as for example, when it is desired to clean out loose material in the bottom of the hole. Although the stabilizers are iluted for by-passage of the drilling mud during the drilling operation, the illites are not ordinarily large enough to pass the loose material or larger pieces which have fallen into the hole or have in some manner become dislodged in the hole beneath the stabilizer. To remove such material it is necessary to either remove the stabilizers from the drill string or cut them away in place, the latter operation being prefered since the former necessitates pulling the pipe from the well. In cutting away the stabilizer body, which is formed of drillable material strong enough to resist lateral deflection of the string within the hole, an overshot having la cutting tool at the lower end thereof is normally lowered down the well over the string and brought into engagement with the stabilizer, following which rotation of the overshot cuts away the stabilizer body. This operation is made diiiicult by the tendency of the stabilizer to rotate with the cutting tool so that the slipping stabilizer blocks such further lowering of the overshot as is necessary to cut away lower stabilizers mounted on the drill collars.

In the prior state of the art stabilizers have been developed which overcome these two diiculties by forming the main body of the stabilizer of a soft elastomeric material which can be easily cut away by a washover tool and by providing within the elastomeric body at a lesser diameter than the outside diameter of the tool, a metal sleeve which has engaging lugs at the bottom end thereof. The lugs are mateable wtih similar upwardly yextending teeth or lugs on the mandrel or collar Ito which the stabilizer is axed. Thus, if the downward force is exterted by the washover tool on the stabilizer it is pressed into non-rotatable engagement with the drill string and the washover tool is allowed to mill away the elastomeric stabilizer body with little difficulty.

It has ben found, however, that such stabilizers are not completely satisfactory, due primarily to the fact that the elastomeric body is necessarily soft in both wearing qualities and longitudinal stiffness. elastomeric material, most generally rubber, is capable of being deformed `suiliciently that some binding effects are sometimes encountered in a tight hole, and in addition the surface of the stabilizer which forms the wear surface is not suiciently resistant to abrasive wear for some stabilizer applications. Another stabilizer of the prior art which attempts to circumvent the above described problems does so by forming the entire stabilizer body out of a relatively soft metal such as aluminum. This metal can, of course, be milled over more easily than a harder steel but such all-metal stabilizers have some disadvantages which are not present in the elastomeric stabilizer. Primarily, such stabilizers have very little cushioning effects since the entire body is formed That is, the n 31,103,391 Patented Sept. 10, 1963 ICE of rigid metal. This cushioning effect has been found to be very desirable in such stabilizers.

Accordingly, it is a primary object of the present invention to provide an improved drill string stabilizer which has an outer contact surface which is resistant to abrasive wear.

It is another object of the present invention to provide an improved drill string stabilizer which utilizes deformable elstomeric material for the cushioning effect inherent in such material.

It is still another object of the present inventon to provide an improved drill string stabilizer which is essentially an elastomeric stabilizer body but which is stiffened and strengthened to an extent not heretofore possible in connection with elastomeric stabilizers.

It is a further object of the present invention to provide such a drill string stabilizer which has wear resistant contact surfaces but which is nevertheless `easily milled or washed over when necessary ina drilling operation.

. It is a still further object of the present` invention to provide such a drill string stabilizervwhich is efcient in use and economical to manufacture.

In its presently preferred form the drill string stabilizer in accordance with the present invention comprises an elongate cylindrical elastomeric body having an outside diameter defining the contact surfaces of the stabilizer.

f Longitudinally extending flutes are provided extending radially inwardly from the outside diameter to define a plurality of circumferentially spaced longitudinally extending passages separated by longitudinal ribs. Positioned within each of the radially extending longitudinal ribs of the stabilizer there is a relatively soft metal insert having the outer surface of the metal substantially coincident with the outside diameter of the stabilizer such that it provides the contact surface of the stabilizer. The inside diameter of the metal inserts is substantially greater than the inside diameter of the stabilizer such that a rubber or elastomeric cylinder is provided between the metal inserts and the inside diameter of the stabilizer. Within the rubber cylinder there is provided a metallic sleeve which is cylindrical in conguration and has engaging lugs at one end thereof.

The novel features which are believed to be characteristic of the present invention both `as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by Way of example. lIt is to be expressly understood, however, that the drawing is for the purpose of illustration and ydescription only and is not intended as a ydelinition of the limits of the invention.

In the drawing:

FIGURE lis a vertical section taken through an illustrative well and showing an exemplary drill string with a Istabilizer in accordance with the present invention mounted thereon;

FIGURE 2 is an enlarged `elevational `view of the stabilizer in accordance with this invention shown partly in section; A

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 2; and p FIGURE 4 is a View in perspective showing one of the metallic inserts which is positioned in the elastomeric stabilizer body.

Referring now to the drawings, there is shown in FIG- URE 1 a stabilizer 20 in accordance with the present invention mounted upon a sub 11 which is connected into the drill string 12 extending within a vertical well hole 14. The stabilizer is substantially cylindrical in conlguration with an inside diameter approximately equal to the outside -diarneter of 1a tubular mandrel 15 which is connected tc an upper extension 16 by a threaded joint 17, the extension and the mandrel together forming the complete sub. The stabilizer is slidably and rotatably mounted with respect to the mandrel and is movable between an upper shoulder 13 formed by the lowerrnost surface of the extension 16 and a lower shoulder formed by an irregular bearing surface 31 on the mandrel 15. FIlhe sub is adapted for connection into the drill string by threaded joints 18 formed at the lower end of the mandrel and at the upper end of the extension 16. It is understood that the sub may be connected into any portion of the drill string, particularly between the dri-11 collars, for stabilizing purposes. A central passage 19 extends longitudinally through the rnandrel and the extension 16 to communicate with similar passages formed in the string 'for flowing drilling mud therethrough.

Referring now particularly to FIGURES 2, 3 and 4, an improved `drill string stabilizer in Iaccordance with the present invention is designated generally as 20 in the figures, and is shown in partial section iu FIGURE 2. The stabilizer comprises in general a rigid sleeve 21 with a length `substantially equal to, but slightly less thian, the overall length of the stabilizer, and which has an inside diameter substantially greater than the inside ydiameter of the stabilizer and the outside diameter of the section of the mandrel upon which the stabilizer is mounted. 'Fhe sleeve is preferably formed with a plurality of perforations extending radially therethrough such that it can be molded integrally with the rubber body portion of the stabilizer as described hereinafter.

The stabilizer includes an elastomeric body portion 22 which is secured to the sleeve 21 through the perf0- rations therein. The elastomeric body is sized for downward reception within the well without substantial interference with the wall thereof, with the maximum outside diameter being large enough to effectively stabilize the drill string against lateral deflection by engagement with the formation wlall following slight lateral stabilizer displacement. Thus, the elastomeric body 22 is cylindrical in configuration with an inside diameter substantially less than the inside diameter of the sleeve 21 and approximately equal to the outside diameter of the mandrel. A series of longitudinally extending grooves 23 lare provided in the inner surface of the body 22 to allow the movement of fluid between the stabilizer and the mandrel suiiicient to form a lubricating film therebetween. The elastomeric body 22 extends outwardly beyond the outer diameter of the sleeve 21 to the outside diameter of the stabilizer at 25 in FIGURE 3. The body is formed with a series of longitudinally extending radial flutes 26 which lare circumferentially spaced about the stabilizer in the outer surface thereof. The flutes 26 therefore divide the stabilizer body into la series of circumferentially spaced protrusions, or ribs, 27 which are sucient in width at the outer diameter 25 thereof to provide the necessary bearing surfaces of the stabilizer. Tihus, the stabilizer body includes longitudinally extending alternate ribs 27 and flutes 26. The purpose of the ilutes is to permit upward passage of drilling iiuid in the well without materially interfering with such flow. The relative circumferentially measured Width of the ribs and ilutes can be readily ldetermined by one skilled in the art.

At the lower end of the sleeve 21 there are provided a series of circumferentially spaced engaging means such as the engaging lugs 30. The lugs lare formed with at least one vertical bearing surface thereon which is mateable with the irregular bearing 31 on the sub. The hearing surface on the sub will be oppositely `directed tto that on the sleeve. Thus, as is wel-l known in the art, if the stabilizer is forced downward into engagement with the sub it is locked in non-:rotatable orientation with respect to the sub. As discussed hereinbefore this is necessary 4 when a washover operation is to be performed in the well. In such `a washover operation it is necessary that lthe overshot ltool nrill or cut away :the ribs 27 of the stabilizer beyond the diameter of the lsleeve 21. That is, the flutes themselves are not suiiicient in size to allow the removal of large bodies land the outer diameter of the ribs completely fills the diameter of the well bole. Thus, if it is necessary to cut away a tool beneath the stabilizer it is essential that the tool can pass over the stabilizer, which is done by milling or cutting away that part of the stabilizer -body extending beyond the sleeve 21.

In accordance with the present invention there is provided in each of the plural-ity of ribs 27 a stiffening wear member 40 formed of a substantially rigid and abrasive resistant material such as aluminum. The material from which the wear members 40 are formed must be sufficiently soft so that it can be milled or cut away by an overshot or similar Washover tool. As shown particularly in FIGURES 2 and 4, each of the wear members 40 comprises longitudinally extending parallel sections 41 and 41a which are spaced apart and are arcuate in configuration. The sections 41 and 41a have exterior surfaces 42 and 42a ,respectively, that coincide in curvature with the outside diameter 25 of the stabilizer. The two vertically extending sections 41 and 41a are spaced apart and connected by bridge members 44.. Hence, the wear members 40 have openings 46 extending radially therethrough in order that the rubber from which the stabilizer body is formed can pass through .the openings 46 `to retain the members 40 in position. The circumferential Width of the sections 41 and 41a is less than half the circumferential width of each rib 27 such that the member 40 when in position in .the rib presents two sufaces 42 and 42a which are :substantially parallel but which are spaced apart. The portion of the body located between the two parallel sections 41 and 41a and radially outward from the bridges 44 is lled with rubber such that .the outside surface of each rib 27 is a composite of rubber and metal. Thus, each rib contains an intermediate surface of rubber 50 separating surfaces 42 and 42a of metal which is more resistant to abrasive wear than the rubber. The radially inner surface 51 of the Wear members is formed with a radius of curvature substantially symmetrical about the center line of the stabilizer. The thickness of the members 40 is such that the inside surface 51 of each member is radially spaced away from the outside diameter of the sleeve 21 by a substantial distance.

Thus, as shown particularly in FIGURES 2 and 3, each of the members 40 is imbedded in a corresponding one of the ribs 27 by molding the elastomeric body about the members. The rubber will flow through the openings 46 and retain the member in position by iilling the entire length of the space existing between the spacedapart sections y41 and 41a of the rib 40. Thus, each of the ribs is, in effect, oating in the elastomeric body and is spaced away from the rigid sleeve. Accordingly, a rubber cushion is provided by the rubber existing between the wear member 40 and the sleeve 21 and between the sleeve 21 and the mandrel.

Accordingly, it can be seen that when it is necessary to mill or cut away the outer portion of the stabilizer in accordance with this inventori, such milling can be easily accomplished due to the configuration of the wear members 40 and the material from which lthey are formed. The fact that a bridge of relatively less thickness than the spaced-apart sections 41a and 41 is used to join the sections makes it possible that an overshot tool will both mill away and fracture the members 4t), causing them to fall as relatively ksmall disengaged parts downward into the well hole. It can also be seen from the description that a stablizer in accordance with this invention presents a bearing surface which is more resistant to abrasion than rubber alone. The bearing surface is comprised mostly of a series of spaced-'apart metal surfaces with some rubber surface existing between the metal. Since the metal in contact with the wall of the Well is isolated from the metallic or rigid parts of the drill string, a cushion is provided against shock being transmitted from the wall of the well to the drill string. In addition, the longitudinally extending wear members Ai@ stiften the rubber body sufficiently that it is not defoimable into a binding condition.

Thus, in normal operation the drill string may be rotated relative to the stabilizer in the Well hole without interference therewith, the stabilizer acting to center the string within the hole. If it becomes necessary to lower a tool, such as a washover tool, within the well beyond the stabilizer, the tool is lowered in the wellto cut away the outer portion of the stabilizer, when the tool comes to rest against the stabilizer, the stabilizer is forced down into non-rotatable position on the mandrel and the further rotation of the overshot causes the outer portion of the stabilizer to be milled away without slippage.

lWhat is claimed is:

1. A drill string stabilizer adapted to be rotatably mounted upon a longitudinally extending cylindrical sub in a drill string and adapted to be :inserted into a well bore comprising: an elongate cylindrical elastomeric body, said body having4 an outside diameter substantially equal to the diameter of said well bore and an inside diameter substantialy equal to the outside diameter of said sub; alternately circumferentially spaced longitudinally extending iiutes and rib sections defined by the exterior surface of said body; a longitudinally extending rigid sleeve positioned within said body, said sleeve having an inside diameter greater than the inside diameter of said body and an outside diameter substantially less than the innermost diameter of said liutes; and a longitudinally extending rigid wear member of drillable metal positioned Within and aliixed to each of said rib sections respectively, each of said members including first and second longitudinally extending circumferentially spaced apart portions dening first and second arcuate surfaces coincident with the exterior surface of said rib, each of said rst and second portions being of equal length substantially equal to the length of said rib sections, each of said wear members including bridge members connecting said rst and second portions, each of said members having a radial thickness defining an interior surface of said member spaced radially outward from the outside diameter of said sleeve. v

2. A drill string stabilizer adapted to be rotatably mounted upon a longitudinally extending cylindrical sub in a drill string and adapted to be inserted into a well bone comprising: an elongate cylindrical elastomertic 6 y body, said body having an outside diameter subst i tially equal to the diameter of said well bore and an inside diameter substantially equal to the outside diameter of said sub; lalternately lcircumierentially spaced longitudinally extending tintes and rib sections deli-ned by the exterior surface of .said body; a longitudinally extended perforated sleeve positioned Within said body, said sleeve having an inside diameter greater than the inside diameter of said body and an outside diameter substantially less than the innermost diameter of said flutes, por-tions of said elastomeric body extending through said perforations in said sleeve; )and a longitudinally extending rigid wear member of drillable material positioned within and -aiixed to each of said rib sections respectively, each of said members including lirst and second longitudinally extending circuferentially spaced apart portions defining iirst and second larcuate surfaces coincident with the exterior surface of the corresponding rib section, each of said irst and second portions being of equal length substantially equal to the length of said rib sections, each of said wear members includ-ing bridge members connecting said rst and second portions, each tot said membershaving a radial thickness dening an interior surface of said member spaced radially `outward from the outside diameter of said sleeve.

3. A drill string stabilizer adapted to |be rotatably mounted upon a generally vertically oriented drill string comprising: an elongate cylindrical elastomeric body having an outside diameter delining the outside diameter of the stabilizer and an inside diameter substantially equal to the portion `ot the string upon which the stabilizer is adapted to be mounted; circumferentially spaced longitudinally extending flutes and rib sections ldelined by the exterior surface of said body; and a longitudinally extending rigid wear member of dnillable material positioned within and latiixed to each of said ribs respectively, each of said members including irst and second iongitltdinally eitending circumferentially spaced apart portions defining tirs-t and second arcuate surfaces coincident with the exterior surface tot the corresponding rib section, each of said iirst and second portions being of equal length substantially equal to the length of said rib sections, each of -said wear members including bridge members connecting said first and second portions.

References Cited inthe file of this patent UNITED STATES PATENTS 2,196,439 Holt Apr. 9, 1940 2,715,552 Lane Aug. 16, 1955` 2,876,992 Lindsay Mar. l0, 1959 

3. A DRILL STRING STABLIZER ADAPTED TO BE ROTATABLY MOUNTED UPON A GENERALLY VERTICALLY ORIENTED DRILL STRING COMPRISING: AN ELONGATE CYLINDRICAL ELASTOMERIC BODY HAVING AN OUTSIDE DIAMETER DEFINING THE OUTSIDE DIAMETER OF THE STABILIZER AND AN INSIDE DIAMETER SUBSTANTIALLY EQUAL TO THE PORTION OF THE DRILL STRING UPON WHICH THE STABILIZER IS ADAPTED TO BE MOUNTED; CIRCUMFERENTIALLY SPACED LONGITUDINALLY EXTENDING FLUTES AND RIB SECTIONS DEFINED BY THE EXTERIOR SURFACE OF SAID BODY; AND A LONGITUDINALLY EXTENDING RIGID WEAR MEMBER OF DRILLABLE MATERIAL POSITIONED WITHIN AND AFFIXED TO EACH OF SAID RIBS RESPECTIVELY, EACH OF SAID MEMBERS INCLUDING FIRST AND SECOND LONGITUDINALLY 